# Dad's Calculator vs Fast Simple Invoice Maker

The clearest difference is in-app purchases: Dad's Calculator at none against Fast Simple Invoice Maker's 4. Dad's Calculator also leads on update cadence (every 2 days vs fortnightly) and iOS requirement (15.0 vs 18.2). On price, ads and device support there is nothing between them.

Both are free to download. Fast Simple Invoice Maker sells 4 one-off in-app purchases. Dad's Calculator asks for nothing beyond the download.

Dad's Calculator ships an update every 2 days, Fast Simple Invoice Maker fortnightly. The most recent releases landed on November 3, 2026 and October 30, 2026 respectively.

## The numbers

| Metric | Dad's Calculator | Fast Simple Invoice Maker |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | **Every 2 days** | Fortnightly |
| Size | 31 MB | 11 MB |
| Requires iOS | **15.0** | 18.2 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Jaehun Kwon](https://appshunter.io/developer/1708326630) | [Eric Savoie](https://appshunter.io/developer/1695096773) |

## What reviewers say

### Dad's Calculator

[App page](https://appshunter.io/ios/app/dads-calculator/id6467169159)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### Fast Simple Invoice Maker

[App page](https://appshunter.io/ios/app/fast-simple-invoice-maker/id6752559476)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Midnight Theme | $0.49 | one-time |
| Forest Theme | $0.49 | one-time |
| Warm Paper Theme | $0.49 | one-time |
| Theme - Ocean | $0.49 | one-time |


## Frequently asked questions

### Is Dad's Calculator free?

Dad's Calculator is free to download, with no in-app purchases.

### Is Fast Simple Invoice Maker free?

Fast Simple Invoice Maker is free to download, with in-app purchases available.

### Do Dad's Calculator or Fast Simple Invoice Maker have ads?

Neither Dad's Calculator nor Fast Simple Invoice Maker shows ads.

### Which is updated more often, Dad's Calculator or Fast Simple Invoice Maker?

Dad's Calculator ships an update every 2 days, and Fast Simple Invoice Maker fortnightly. Most recently, Dad's Calculator was updated on November 3, 2026 and Fast Simple Invoice Maker on October 30, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*